The rising interest in electrical properties of single molecules is triggered by physical properties that emerge at the transition between the atomic and the bulk scales. Moreover, there is a strong possibility that building blocks of future electronic devices will be found in such systems. One key challenge is attaching probes to nanometer size objects. Early methods to produce nanometer-size gaps (“nanogaps”) were complex and provided a low yield. These include standard electron-beam (e-beam) lithography, break junctions, carbon nanorods, electrochemical growth, and electromigration.
As commercial integrated circuit design rules begin to incorporate sub-100 nm critical dimensions, the possibility of electronic devices based on single molecules is being widely considered. At this time, it has become possible, to make and measure the properties of electrical circuits containing one or a small number of molecules. Thus, in order to create such circuits, making molecular-scale gaps or nanogaps in an otherwise continuous metal, is necessary. If a molecule can be designed to attach itself across this gap, or if it can be drawn into the gap in some other way, a circuit results. This is the first step towards functional electronic devices containing many integrated molecules.